Duplex wave signaling system



H. M. LEWIS DUPLEX WAVE SIGNALING SYSTEM Oct; 23, 1928. I 1,688,872

Filed Aug. 14.1920 2 sheets-sheet 1 S14/venten bu/bow, QAM) Oct. 23, 1928. 1,688,872

H. M. Ll-:wls

DUPLEX WAVE SIGNALING SYSTEM Filed Alllg. l4 1920 2 Sheets-Sheet 2 l aerfaon` AMPLIFIER asrfcrof? '5) @MME '-yawma Patented (let 23, 1928.

`iJNl'l'ED STATES 'HAROLD lVI. LEWIS, 0F LONG BRANCH, NEW JERSEY.

DUPLEX WAVE SIGNALING SYSTEM.

Application filed August 14, 1920.

It has heretofore been the general practice in wave signaling systems to effectively isolate, so to speak, the receiving apparatus from the transmitting apparatus at t-he same station. taneous radio transmission and reception systems, to provide aso-calledbalancebetween the transmitting apparatus and the receiving apparat-us at the saine station in order that the energy produced at, or radiated by,`

the transmitter shall not be. effective on, nor interfere with the independent functioning` of the receiving apparatus. It is well known that an absolute balance between the transinitter and receiver at the same station is difficult to obtain, while rough or approximate balances may be readily effected in various well known ways.

One feature of the present invention is that it does not require an absolute balance to be maintained between the transmitter and receiver at the same station, since a portion of the energy produced at the transmitter is supplied to the receiver for the actuation and operation of the receiving apparatus. The invention involves, however, the use of a rough or approximate balance between the transmitter and receiver at the same station vso that the amount of energy obtained from the transmitter may be regulated and supplied to the receiving apparatus in the proper amounts, In this connection it is contemplated to utilize a continuous or undamped wave transmitter opera-ting continuously, to provide local high frequency oscillations for reception purposes when notl being used for the transmission of signals.

Another feature of the invention conteniplates the use of the local continuous oscillations obtained in the proper' amounts from the transmitter, for the purpose of combining such oscillations with the incoming energy to produce a. beat frequency or readily amplifiable high frequency above good audibility in the manner set forth in UnitedStates Patent No. 1,342,885. Briefly, the method of reception disclosed in this patent consists in converting the frequency of the incoming oscillations down to some predetermined and lower value of readily-amplifiable high frequency oscillations above good audibility which may then be amplified and finally detected and indicated to render the voice or audio frequency modulations audible. the reception of unmodalat-ed continuous waves, sinne form of chopper or the 'usual It has also been proposed in simul- Serial No. 403,560.

audible-beat heterodyne methods may be used to produce an audible note in the telephone receivers, or to furnish a rectified or pulsating current to an indicating instrument. As is well known, this method of using a beat frequency produces no appreciable distortion of the incoming signal energy, and hence makes possible the reception of radio-telegraph and radio-telephone signals in a particularly clear and easily readable manner.

It has been pointed out that the invention contemplates the continuous production of energy at the transmitter in order that a receiver at the same station may be supplied with the proper amounts of the necessary local continuous oscillations of suitable strength and frequency for the reception of signals from a distantly located transmitter. If, therefore, two distantly located stations each comprising a transmitter and receiver, and each using the same beat or third high frequency above good audibility is selected for use at each station, the stations will be found to be mutually dependent one upon the other, to the extent that the stopping of either transmitter will be noted at both receiving stations. The reason for this is that energy from a. distant transmitter which is assumed to be continuously radiating energy but not transmitting signals, may under certain conditions be received on the antenna of the local station which is assumed to be transmitting. Since the energy of the distant station and the energy of the local transmitter is effec-tive upon the local receiver, the two frequencies will be combined in the local receiving apparatus `to produce the chosen third frequency which is above good audibility. In this way signals transmitted from either station will be heard both at the local station and at the distant receiving station. ln order that this simultaneous or duplex operation of the two systems may be effected, it is necessary that the frequencies of transmission of the two stations differ by the frequency selected as the beat frequency at both receiving stations.

When twostations are operating in the manner above described,'both having chosen the same beat frequency, it is possible for either station to break or interrupt the other instantaneously.

By the expression frequency above goo audibility is meant a frequency which, i l ile it may still be audihio, is of Stich high that it does not impair' the reproduction of speech.

Various suitable arrangements tor making a. portion of the energy produced at a trans mitter eiiective upon a receiver at the same station, and for utilizing the same or associated antenna under certain conditions for simultaneous transmission and reception purposes, as well as other features and advantages of the invention, will be understood from a consideration ofthe following descrip tion in conjunction with the drawings, in which:

Fig. 1 illustrates the use of two associated antennae for transmitter and receiver, respectively, at the same station;

Fig. 2 illustrates an arrangement of transmitter and receiver in which loop antennae are utilized; y

Fig. 3 illustrates the use of two coupled loop antennae for transmitter and receiver, respectively, having means for varying the balance therebetween;

F igmi illustrates the use ot a single loop for the purposes of both transmission and reception and having means for varying the balance between the transmitter and receiver circuits at the same station;

Fig. 5 illustrates the use of a single antenna earth system for both recept-ion and transmisison; and y Fig. 6 illustrates the use of` a single loop antenna for both transmitter and receiver which is a special application useful for short distances and extremely short wave lengths.

In Fig. 1 the antenna earth system 1, 2 may be considered as representing a transmitting station comprising the antenna, including the loading inductance 3, and having a continuous wave generator 4. Any well known means for modulating the energy radiated in accordance with signals to be transmitted may be utilized. The receiving system at the same station comprises the antenna earth system 5, 6, the loading inductance 7 and primary condenser 8. The antenna system 5, 6 is adapted to be brought into resonance with the received waves by means of the inductance 7 and condenser 8. The usual secondary circuit 9, 10 is also tuned to t-he frequency of the received waves. 11 is a rectifier for the purpose of converting the combined incoming energy and local oscillations obtained from the associated transmission system 1, 2, 3, 4 to produce continuous oscillations of a third high frequency above good audibility in the circuit 12, 13-the capacity 12 and inductance 13 being of proper values to bring the circuit into resonance with the frequency of the oscillations of the said third high frequency. Associated with the circuits 12, 13 is the circuit 14, 15 tuned to the same high frequency as the circuit 12, 13. The second circuit is provided with a second rectifier 16 for the purpose' of detecting the oscillations of the well known manner. If unmodulated con.

tinuous waves are to be received, the switch 18 may be opened to effectively place in cir cuit with the rectifier 16, some form of chopper 19 in order that an audible note may be produced in the telephones. If :it is desired, however, a second local source of high frequency oscillations may be provided, such as the source 19 for combining the third or superaudible high frequency oscillations with the local oscillations in the manner of the well known audible-beat heterodyne. When the ocal source 19 is employed, the switch 18 should shunt the chopper or tikker 19.

In the operation of the transmission and reception system of Fi 1, it is necessary that a generator of hig frequency oscillations of a suitable frequency be provided and that it be maintained in continuous operation at the transmitter. In this connection, there is no limitation as to what the fre uenoy of the oscillations so generated should Je except that the frequency should be above good audibility and chosen in such a manner as to differ from the frequency of the incoming oscillations to he received, by a third high frequency which is also above good audibility and preferably a readily-amplifiable high frequenc Care should also be taken to so associatet 1e antenna earth systems 1, 2 and 5, 6, respec tively, so that only a portion of the energy produced at the transmitter shall be made ei'ective upon thereceiving apparatus associated with the antenna earth system 5, 6.

In Fig. 2 a transmission and reception system is illustrated which is substantially similar to that described in connection with Fig. 1. In Fig. 2, however, the antenna earth systems have been replaced hy loop antennae 20, 21, respectively, the generator 22, condenser 23 and loop 2() forming the transmission system. As in the case of Fig. 1, the loop 21 is suitably associated with the loop 2O so that a portion of the energy produced by the generator 22 at the transn'xitter, shall be made effective upon the receiving apparatus associated with the loop 21 of the receiving system. A rectifier 11 is associated with the receiving antenna and a circuit 12. 13 is provided which is tuned to the third high frequency obtained by combining the incoming energy with the oscillations oh tained from the transmitter. A high fre quency amplifier 25 adapted to amplify the third high frequency is interposed between the detector 11 and the second detector 26, thereby making the receiving system particularly effective on weak short wave signals.

In Fig. 3, a rough balance is obtained be tween the transmitting loop antenna 2S an-d the receiving loop antenna 29 by means of a variable coupling 30. In this way, an optimum value of heterodyne energy may bc obtained from the nransmitting` system, comprising the generator 31 and the loop antenna 28. The energy so obtained is made effective upon the receiving system, comprising the loop 29 and the tuning condenser 32. A vacuum tube detector 33 is utilized for converting the'combined incoming energy and local oscillations to produce a third high frequency in the circuit 34, 35. The circuit 34, 35 is directly coupled to a high frequency vacuum tube amplifier 36 which amplifies the third high or super audible frequency. A second vacuum tube detector 37 is provided for detecting the resulting oscillations. The resulting oscillations are indicated by means of the telephones 38.

In Fig. 4 a single loop antenna 39 is utilized in connection with a coupling balancing arrangement 40, for both transmitter and receiver. The proper amount of energy produced by the generator 41 is made effec-- tive upon the receiving apparatus through the loopl 39 and the coupling 40. As in the case of Fig. 3 a vacuum tube detector 42 is provided for converting the combined incoming energy and local high frequency oscillations to produce oscillations of a third high frequency above good audibility in the circuit 43, 44. The circuit 43, 44 is directly coupled to a vacuum tube high frequency am plifying system 45. The resulting amplified oscillations are detected by the vacuum tube detector 46 and indicated by the telephones 47.

Fig. 5 shows one of the more preferred forms of the invention wherein a single antenna earth system 48, 49 is employed. The antenna is divided into two parallel branches each of which includes a variable oscillatory circuit 50, 51. The oscillatory circuit 50 is preferably tuned to the frequency of the incoming signals, thus causing it to block the pas-sage of incoming signals through that branch of the antenna. Then thus adjusted, however, the oscillatory circuit 50 is anti-resonant to the Alocal transmitter energy, thus offering low impedance thereto and permitting the latter to flow through, since the frequency of the local transmitter always differs from that of the incoming signals by a frequency above good audibility. The oscillatory circuit 51 is tuned to a point wherein it is nearly resonant to the local transmitter energy and anti-resonant to the incoming signals. It will, therefore, be seen that the incoming signals will pass freely through that branch of the circuit including the oscillatory circuit 51, while only a small portion of the local transmitter energy will pass through that branch. In this figure the local transmitter is represented by the character 52, while characters 53, 54 and 55 represent symbolically the first detector, amplifier, and the second detector circuits of the receiver,

The circuits thus represented symbolically may correspond with circuits 42, 45 and 46 respectively of Fig. 4. Reference character 56 represents a pair oftelephone receivers.

In Fig. 6, a circuit is shown which is useful for extremely short wave lengths and distances, limited by the strength which the oscillations may have, for a single tube generator, 58, to function well as both a transmitter and receiver. Nhen the loop 57 is utilized for the radiation of signal energy, the vacuum tube 58 serves as an oscillator and generates undamped oscillations continuously. rllhe voice currents produced in the circuit 62 by the transmitter 63 are directly supplied to a circuit associated with the oscillating system including the tube 58 in order that the energy radiated by the loop antenna 57 may be modulated in accordance with the voice. currents inthe usual manner. When the loop 57 is used for reception purposes, the vacuum tube 58 serves as an oscillator rec'- tifier and furnishes the local energy for combining with the incoming energy as well as converting the combined incoming and local energy to produce a third readily-amplifiable high frequency above good audibility. The readily-amplifiable high frequency oscillations are amplified by the high frequency vacuum tube `amplifying system 59 and are detected and indicated respectively by the vacuum tube 60 and the telephone 61.

In all of the various systems as described in connection with the different figures of the drawings, if it is contemplated that one of the above described systems be used at a given station, it is only necessary that the undamped oscillations produced at the transmitter be generated continuously during both the transmission of signals and during periods of reception, and-the frequency of these oscillations should be such that upon combining them with the incoming energy, a third high frequency above good audibility preferably a readily-amplifiable high frequency, shall be produced. Beyond this requirement there is no other limitation as to what the frequency of the oscillations produced at the transmitter shall be. If, however, the use of two stations each comprising a system as shown in one of the figures of the drawing, be used, it is desirable that the frequencies of the oscillations produced at the respective transmitters of the two stations differ by the frequency which has been4 selected as the third high frequency. For example, if the frequency selected as the third high frequency be 100,000 cycles, and the frequency selected as one of the transmission frequencies be 1,000,000 cycles, then it will be necessary that the other transmission frequency be 900,000 or 1,100,000 cycles.

It should also be noted that the reception of the modulated continuous wave energy is accomplished without lthe distorted ltone which invariably results when the ordinary form of audible-beat or audible-heterodyne reception is employed. Furtherthis system is inherently more stable in operation than the usual audible-heterodyne systems, since a variationin either the frequency of the local oscillations or the incoming oscillations will produce proportionately less difference in the resulting third high frequency than wouldV bc the case if an audible beat note Were employed. The reason for both of these phenomena is rather involved and in any case unnecessary, as it is an easily demonst-ated experimental fact.

I claim:

l. The method of receiving the incoming energy in a Wave signaling system, which comprises making a portion of the energy produced at a local transmitter effective upon the receiving apparatus at the same station to provide a local source of high frequency oscillations, combining said local oscillations with the incoming energy to produce oscillations of a third high frequency above good audibbility, and detecting and indicating the said third high frequency oscillations.

2. The method of receiving the incoming energy in a Wave signaling system, which comprises making a portion of the energy produced at a continuously operating undamped wave transmitter eff-ctive upon the receiving apparatus at the same station to provide a local source of high frequency oscillations of a frequency differing from said incoming oscillations by a third readilyamplifiable high frequency above good audibility, combining said local oscillatons with the incoming energy, converting the said combined energy to produce said third high frequency oscillations7 and detecting and indicating the said third high frequency oscillations.

3. The method of receiving the incoming energy in an unmodulated undamped wave signaling system, which comprises making a portion ofthe energy produced at the transmitter effective upon the receiving apparatus at the same station to provide a local source of high frequency continuous oscillations differing from said incoming oscillations by a third readly-amplifiable high frequency above good audibility, combining said local oscillations with the incoming energy, converting the combined energy to produce oscillations of the said third high frequency, combining said third high frequency oscillations with locally generated high frequency oscillations of a frequency at or near to the said third high frequency, converting the last said combined energy to produce low7A frequency oscillations and indicating the resulting low frequency oscillations.

Li. The method of permitting simultaneous transmission and reception of radio signals on the same or associated antenna which comprises making a portion of the energy produced at the transmitter effective upon receiving apparatus at` the same station to provideV a local source of high frequency oscillations, combining said local oscillations with the incoming energy to produce oscillations of a third high frequency above good audibility, and detecting and indicating the said third high frequency oscillations.

5. The method of permitting simultaneous transmission and reception of radio signals on the same or associated antenna Which comprises malring a portion of the energy produced at a continuously operating undamped Wave transmitter effective upon the receiving apparatus at the same station to provide local source of high frequency oscillations, combining said local oscillations with the incoming received energy to produce oscillations of a third high frequency above good audibility, and detect-ing and indicating the said third high frequency oscillations.

G. The method of permitting simultaneous transmission and reception of radio signals on the same or associated antenna Which comprises making a portion of the energy produced at the transmitter effective upon' the receiving apparatus at the same station to provide a local source of high frequency oscillations differing from the frequency of the incoming energy by a third readily-amplifiable high frequency above good audibility, combining the said local oscillations with the incoming received energy to produce said readily-amplifiable high frequency oscillations, amplifying the said third high frequency oscillations and detecting and indieating the resulting amplified oscillations.

7. The method of permitting simultaneous transmission and reception of unmoldulated undamped Wave radio signals on the same or associated antenna which comprises making a portion of the energy produced at an undamped Wave transmitter effective upon receiving apparatus at the same sta-tion to provide a local source of high frequency oscillations, combining said local oscillations with the incoming received energy, converting the combined energy to produce oscillations of a third highfrequency above good audibility,

combining said third high frequency oscillations with locally generated high frequency oscillations of a frequency at or near said third high frequency, converting the said last combined energy to produce loiv frequency oscillations and indicating the resulting low frequency oscillations.

8. The method of permitting simultaneous transmission and reception of short Wave radio telephone signals on the same or associated antenna which comprises making a portion of the energy produced at an undamped wave voice modulated transmitter effective upon receiving apparatus at thesame station te provide a local source' of high frequency oscillations differing fromthe incoming energy by a third readily-amplifiable high frequency above good audibility, combining said local oscill ations with the incoming enerfcy, converting the combined energy to produ ce the third readily-ampliiiable,high frequency oscillations, amplifying the said third high frequency oscillations, and detecting and indicating the resulting ampliiiable oscillations.

9. rlhe method of communicating between two distantly located wave signaling system stations which comprises utilizing oscillations of a given frequency at one stations transmitter and oscillations of a frequency differing from said lirst mentioned oscillations by a third high frequency above good audibility at the otherof said stations transmitter, and producing in each stations receiver said third high frequency oscillations, and detecting and indicating at each station the said third high frequency oscillations.

10. In a wireless telephone system, a pair of distantly located stations each comprising a transmitter and a receiver, each transmitter including a source of radio frequency continuous oscillations, the difference between the operating frequencies of said transmitters being a frequency above good audibility, and means at each receiver for coordinating the high frequency waves from both transmitters to provide a beat frequency equal to said frequency above good audibility.

11. In a wireless telephone system, a pair of distantly located stations each comprising a transmitter and a receiver, each transmitter including a source of radio frequency continous oscillations, the difference between the operating frequencies of said transmitters being a beat frequency above good audibility, and means at each receiver for detecting and indicating the signal components of said beat frequency.

12. The method of receiving the incoming energy in a modulated continuous wave signal'ing system, which comprises making a portion of the energy produced at the transmitter effective on the receiving apparatus at the same station to provide a local source of continuous high frequency oscillations diffen ing from the frequency of the incoming energy by a third readily amplifiable high frequency above good audibility, combining said local oscillation with the incoming energy, converting the said combined energy to produce the said third frequency oscillations and detecting and indicating the said third frequency oscillations.

13. The combination in a signaling system of a station comprising a high frequency continuous wave receiver, a high frequency continuous wave transmitter, means for establishing an approximate balance between said transmitter and said receiver whereby a portion of the high frequency energy generlll. rlhe combination in a signaling system of two stations adapted for inter-communication, each station comprising a high frequency continuous wave receiver and a high frequency continuous wave transmitter, the difference between the operating frequencies of said transmitters being equal lto a third fresse-11W above good weimar,

means for impressing a portionof the high frequency energy generated by the transmitter at each station upon the receiver lat the same station, means for varying the percentage of energy thus impressed upon the receiver at each station, means included in each receiver for combining the energy impressed thereon from both said transmitters to .produce beat frequency oscillations having a frequency equal to said third frequency above good audibility, and means ineluded in each of said receivers for detecting and indicating said beat frequency oscillations.

- l5. In a high frequency signaling system,

a station comprising a transmitter including a generator of high frequency electrical oscillatory energy, a receiver, means for impressing a portion of the oscillatory energy from said generator' upon said receiver', means for adj ustably varying the percentage of said oscillatory energy thus impressed upon said receiver, means included in said receiver for combining said oscillatory energy with incoming oscillatory energy having a frequency differing from said first-mentioned oscillatory energy by a third readily amplifiable high frequency above good audibility, means for converting the combined energy to produce said third readily ampliliable high frequency, means for amplifying said third high frequencyoscillations, and means for detecting and indicating said third high frequency oscillations.

16. The method of duplex signaling which comprises transmitting in one direction between two stations an audibly modulated carrier wave, transmitting in the other direction an audibly modulated carrier wave of different frequency, and utilizing at one of said stations a port-ion of the energy of the outgoing carrier wave to produce an auxiliary carrier wave having a frequency differing from each of said waves.

17. The method of duplex signaling which comprises transmitting messages in one direction between two stations by means of a carrier wave, transmitting a message in the loo other direction upon a carrier Wave of a different frequency, utilizing at one of said stations a portion of the energy of the outgoing carrier Wave to reinforce the incoming signal.

18. A radio system comprising a. station having an incoming Wave receiving circuit, a source. of high frequency carrier Waves for transmitting outgoing signals, means for combining Waves fro-m said source with incoming Waves whereby inaudible Waves of a frequency different from either of said frequencies are produced, and means for deriving audible inconiing signals from said last mentioned Waves. y

19. A system for duplex naling having means for producinga beat requfency Wave vWhich is equal to the difference of the frequencies of the incoming and outgoing carrier Waves and which is modulated in accordance with the incoming and the outgoing signals, and means for selecting and detecting said Wave.

20. The method of duplex signaling which comprises transmitting a carrier wave in one 'direction between tivo stations, transmitting a vcarrier Wave of different frequency in the otherfdi'rec-tion, and utilizing a po-rtion of the lenergy of the outgoing `carrier Wave. at one of said stations in combination with the incoming carrier Wave to produce an auxiliary carrier Wave having a frequency above the usual audiblev range.

`21. The method of 'signaling which comprises generating a carrier Wave for outgoing transmission, receiving an incoming carrier Wave, and combining said carrier Waves to produce a combination frequency Wave having a frequency above the usual range of audible sound frequencies.

22. The method of signaling which comprises generating a carrier Wave for outgoing transmission, receiving an incoming carrier Wave, and combining said carrier waves to produce a combination frequency Wave having a. frequency abovetlie usual range of audible sound frequencies, but lia-ving an amplitude variationat an audible frequency.

23. A signaling systemwhich comprises ieans for `generating and transmitting to a distant station energy of an outgoing Wave frequency, lneans for receiving Wave energy of an incoming Wave frequency, means for continually producing during transmission and reception a Wave having a frequency above the usual audible ran-ge by combining energy of the outgoing and incoming wave frequencies and means for select-ing the e'nergy of the continually produced Wave.

24:. A two-Way signaling system comprising means lfor receiving and combining `the energy of an incoming carrier vva've With energy of the outgoing carrier 'Wave frequency, selecting a component of the resultant energy, land detectinu the selected component to produce inaudible frequency Wave.

In testimony whereof I affix my signature.

HAROLD M. LEWIS. 

